The link you which you are referring(http://wiki.alfresco.com/wiki/Forms_Developer_Guide#Introduction) is specific to Alfesco Share. In alfresco explorer there is only server side validation for constrain no client side validation done. In Alfresco Share you can see all the underlying files though Spring Surf Bug tool.
I am using Alfresco Share. What is the name of the javascript file (used in the browser) that will contain the regex constraint I defined in my model. I wish to confirm that my regex constraint is actually being sent to the browser client.